Cigarette smoking is the most prevalent form of tobacco use today, and its health risks are well known. Smoking is considered the foremost preventable cause of excess deaths in the United States. Despite the well-publicized deletrious consequences of cigarette smoking, a detailed analysis of its effects at the molecular level is limited by the many hundreds of gaseous and particulate constituents known to be present. Some components of cigarette smoke has been shown to alter DNA replication and/or repair in tissue cultured cells. Because nicotine is the major component in the particulate phase of cigarette smoke and is the most powerful pharmacological agent in smoking, and because cell proliferation is coupled to the DNA synthetic rate, we propose to study the detailed interaction between cigarette smoke, nicotine and DNA expression, using established mammalian cell lines. Specifically, the role of cigarette smoke or nicotine on overall and specific changes in DNA synthesis will be investigated in an attempt to correlate changes in these macromolecular parameters to alterations in mammalian cell proliferation. These goals will be accomplished by (i) in vivo pulse labeling with radioactive precursors, (ii) density gradient centrifugation, (iii) column chromatography and (iv) determining changes in nucleoid sedimentation. These studies are expected to provide a better understanding of the molecular events which are associated with the exposure of mammalian cells to cigarette smoke or nicotine. Results of this investigation should be useful for detection of cigarette smoke or nicotine-induced genotoxicity for the population at large and should aid in our battle against the undesirable effects of cigarette smoking.